Skip to main content
Version: v0.3.3

rgbfix(1) — Game Boy checksum fixer

rgbfix [-CcjsVv] [-i game_id] [-k licensee_str] [-l licensee_id] [-m mbc_type] [-n rom_version] [-p pad_value] [-r ram_size] [-t title_str] file

The rgbfix program changes headers of Game Boy ROM images. It also performs other filetype operations, such as truncation. The arguments are as follows:

Set the Game Boy Color–only flag: 0x143 = 0xC0. If both this and the -c flag are set, this takes precedence.
Set the Game Boy Color–compatible flag: 0x143 = 0x80. If both this and the -C flag are set, -C takes precedence.
game_id
Set the game ID string (0x13F–0x142) to a given string of exactly 4 characters. If both this and the title are set, the game ID will overwrite the overlapping portion of the title.
Set the non-Japanese region flag: 0x14A = 1.
licensee_str
Set the new licensee string (0x144–0x145) to a given string, truncated to at most two characters.
licensee_id
Set the old licensee code, 0x14B, to a given value from 0 to 0xFF. This value is deprecated and should be set to 0x33 in all new software.
mbc_type
Set the MBC type, 0x147, to a given value from 0 to 0xFF.
rom_version
Set the ROM version, 0x14C, to a given value from 0 to 0xFF.
pad_value
Pad the image to a valid size with a given pad value from 0 to 0xFF. rgbfix will automatically pick a size from 32KiB, 64KiB, 128KiB, ..., 8192KiB and give a warning thereafter. The cartridge size byte (0x148) will be changed to reflect this new size.
ram_size
Set the RAM size, 0x149, to a given value from 0 to 0xFF.
Set the SGB flag: 0x146 = 3.
title
Set the title string (0x134–0x143) to a given string, truncated to at most 16 characters. It is recommended to use 15 characters instead, to avoid clashing with the CGB flag (-c or -C). If both this and the game ID are set, the game ID will overwrite the overlapping portion of the title.
Print the version of the program and exit.
Validate the header and fix checksums: the Nintendo character area (0x104–0x133), the header checksum (0x14D), and the global checksum (0x14E–0x14F).

Most values in the ROM header are only cosmetic. The bare minimum requirements for a workable image are checksums, the Nintendo logo, and (if needed) the CGB/SGB flags. It is a good idea to pad the image to a valid size as well (“valid” meaning a multiple of 32KiB).

The following will make a plain, no-color Game Boy game without checking for a valid size:

$ rgbfix -v foo.gb

The following will make a SGB-enabled, color-enabled game with a title of “foobar”, and pad it to a multiple of 32KiB. (The Game Boy itself does not use the title, but some emulators or ROM managers might.)

$ rgbfix -vcs -l 0x33 -p 0 -t foobar baz.gb

The following will duplicate the header (sans global checksum) of the game “Survival Kids”:

$ rgbfix -cjsv -k A4 -l 0x33 -m 0x1B -p 0xFF -r 3 -t SURVIVALKIDAVKE SurvivalKids.gbc

rgbasm(1), rgblink(1), rgbds(7)

rgbfix was originally released by Carsten Sørensen as a standalone program called gbfix, and was later packaged in RGBDS by Justin Lloyd. It is now maintained by a number of contributors at https://github.com/rednex/rgbds.